Dental alloy for cast dentures



Patented Get. 10, 1933 DENTAL ALLOY FOR CAST DENTURES Robert Ross Bayes,London, England, assignor to Baker & Company, Inc., Newark, N. 3., acorv poration of New Jersey No Drawing. Application eb-airy 4, 1935Serial No. 655,251

2 Claims. (Cl. 75-1) This invention relates in general to alloys, andmore particularly to an alloy especially suitable for use in making castmetal dentures.

Metal bases for dentures, such as plates,

5 bridge work saddles and backings, are frequently made by casting, butmany metals and alloys which have been used heretofore for that purposeare objectionable for various reasons. Some metals and alloys are. tooexpensive, many do not melt into completely liquid state, but rathertend to puddle so that perfect castings cannot be made, while some aretoo soft or lack adequate strength to withstand use in dentures; manycannot be satisfactorily polished, many quickly tarnish or oxidizeespecially under influence of the oral fluids, and some deleteriouslyaffect the tissues of the oral cavity. Many known alloys which wouldotherwise be satisfactory, have such high melting points beyond theusual range of temperatures avail able in dental laboratory practice,that such alloys are impracticable-for use. Some known alloys also areheavy, which is objectionable in a dental casting where a minimum ofweight consistent with the necessary strength, is greatly to be desired,if not a prime requirement.

It is also highly desirable that a metal base for a denture be asinconspicuous as possible, and accordingly an allow that is light orsubstantially white in color and which will take and retain a highmirror-like polish to reflect the color of the oral tissues isespecially advantageous; many known alloys do not possess thesequalities.

Therefore, one object of my invention is to provide a novel and improvedalloy. and especially such an alloy for making dental castings, whichshall be relatively inexpensive and from which a casting substantiallyperfect as to form and as to strength, appearance and hygienicproperties required in a dental casting. can be made with the knowledge,facilities and equipment usually available in the average dentallaboratory.

Other objects of my invention are to.pr0vide an alloy and especially .analloy for making dental castings, which shall be inexpensive, whichshall have a relatively low melting point well within the usual range oftemperatures available in dental laboratory practice, which shall meltcleanly into complete liquidity and shall not puddle, which shall besufliciently hard and strong to withstand all strains incident to normaluse in dentures, which shall be capable of taking and retaining a high,mirror-like polish, which shall be substantially white in color, whichshall have high resistance to oxidation, especiallyto prevent materialtarnishing underinfiuence of oral fluids, which shall notdeleteriouslyaffect or injure'the tissues of the oral cavity, which shall have a lowspecific gravity and be light in weight as compared to alloys used todayfor dentures, and which shall be capable of being practically perfectlycast into any desired shape; and to 011- 5 tain other advantages andresults as will be brought out by the following description.

I have discovered that an alloy of gold, palladium, silver, copper andzinc is admirably adapted for metal bases for dentures and to accomplishall of the foregoing objects and attain the above-mentioned advantagesand results. Satisfactory alloys can be produced from these metals,gold, palladium, silver, copper and zinc,

combined in various proportions, but I have found that the mostdesirable alloys may contain from ten (10) percent to twenty (20).percent of gold, twenty (20) percent to thirty (30) percent ofpalladium, forty (40) to fifty (50) percent of silver, eleven (11) toeighteen (18) 8 percent of copper and one (1) to four (4) per-' cent ofzinc, the proportions within said ranges being variable to produce manydifferent combinations. An especially satisfactory alloy is composed offifteen parts of gold, twenty-four parts ofpalladium, forty-five partsof silver, fifteen parts of copper and one and one-quarter parts ofzinc. Alloys composed of gold, palladium, silver, copper and zinc, inthe proportions above stated, are relatively inexpensive, for example,the cost of such alloys is from one-half to one-third the cost of knownalloys containing a major portion of gold, and at the same time alloysmade according to my invention have high chemical. resistivity and donotmaterially oxidize or tarnish, especially under influence of oralfluids. Moreover, my alloy has a melting point considerably below thatof pure gold, well within the range of temperatures available intheaverage dental laboratory, and the alloy freely melts into acompletely liquid state, so that castings substantially perfect in formcan be produced with ease by the average dentist or dental technicians.

Furthermore, my alloy has adequate strength to retain any shape intowhich it is formed and to resist the strains incident to use indentures, and it is sufficiently hard to take and retain a mirror-likepolish." The alloy also is substantially white or platinum-like in colorand when high- 1y polished is capable of reflecting the color of theoral tissues so that the alloy will be inconspicuous in the mouth. Also,while the alloy contains precious metal, it has a comparatively lowspecific gravity, i. e., less than 12, so as to ensure a minimum ofweight of metal in a precious metal base for dentures; and the alloy ishygienic and sanitary and does not deleteriously affect the oral tissuesThe gold and palladium apparently bring resistivity to chemical action,oxidation and tarnishing, while the silver seems to facilitate themelting of p the alloy into a completely fluid state, and possiblyincreases the hardness of the alloy, the copper adds hardness andappears to lower 7 the melting point of the combined gold, silver andpalladium, and the zinc probably provides further resistance totarnishing and lowers the melting point of the alloy.

While I have described specific proportions of the metals constitutingmy alloy, I do not wish.

1,oso,11e

to be understood as limiting myself to specific proportions of themetals except as required by the following claims when construed in thelight of the prior art. Furthermore, other metals having propertiessimilar to those of the metals described may be utilized withoutdeparting from the spirit or scope of the invention.

Having thus described my invention, what I claim is:

1. An alloy composed of from ten (10) percent to twenty (20) percent ofgold, from twenty (20) percent to thirty (30) percent of palladium, fromforty (40) percent to fifty (50) percent of silver, from eleven (11)percent to eighteen (18) percent of copper, and from one (1) percent tofour (4) percent of zinc.

2. An alloy for dentures composed of fifteen parts of gold, twenty-fourparts of palladium, forty-five parts of silver, fifteen parts of copperand one and one-quarter parts of zinc.

ROBERT ROSS BAYES.

